Stoker grate block



Oct. 11, 1938. H. E. PRESTON STOKER GRATE BLOCK Original Filed March 22, 1928 v 4 Sheets-Sheet l H. E. PRESTON STOKER GRATE BLOCK Oct. 11, 1938.

OriginalFiled March 22, 1923 '4 Sheets-Sheet 2 ------sF- 1 if II n 1m am. 1 z y m W w x a Oct. 11, 1938. H. E. PRESTON STOKER GRATE BLOCK Original Filed March 22, 1923 4 Sheets-Sheet 4 I lllltrpdllllv I Ail jmwfor Patented Oct. 11, 1938 -a-srm'res .STOKER-"GRATEY'BLOCK 2 Herbert Preston-g Philadelphia? Pa; .assignor -to :LAmerican-Engineering Gumpanyy-Philadelphia,

- Pa., amorporation-of Pennsylvania Griginal application March 22; "1928, Serial No. -263,900. Patent-No. 081,067,datedMay 18, a 1937. -Divide'd and this" application 'Februa-ry 12,1936, Serial-No;s;63,544

v 12'L'Glaims.

This invention: relates to lower grates for stoker-furnaces, and-:more particularly-to the gratezblocks employed on suchde'vices.

:One .object of'ztne present invention is to pro- .videa generally improved grate block construction which is adaptedto be secured-tonithe sup- .porting iramework without the use of bolts, keys, :01100118115613213138 fasteningrmeans, the parts he- --ingsuch that they mayz-be-easily renewed with -mi11imum. disturbance. to adjacent portions :or; the .stoker.

'eAnother vobject: is: to provide anrimproved 'grate :block construction having means provided ithere- ..'on for. distributing the air. into. the furnacazand .also'having cooling fins. providedJthereon, where- :by. the blocks are:maintainedrrelatively cool during-operation oiathe furnace.

.Other objects of: myrinventlonswill' becomeiapparent more fully hereinafterwhen takentinxcon- -nection. with the accompanying; drawings herein.

Fig.;1 ..is alongitudinal: sectional view taken through the lower end of atstoker :furnace; show- -ing; the.--grate :blo'cks-comprising the present .invention assembled upon the supporting structure ofthe lower grate.

Fig. 2. is an. enlarged detail longitudinal sectional view of the stationary. lower grate ''structure: and theanti-irictiona supportingmeans for the. lower end of-the-stee1 supporting beams, the :sectional planebeing taken on line-242 of- -Fig."3.

.Fig.13 is a-transverse sectional viewtaken on =line-"3i3.of'Fig.:2.

FFig; e 1 is a horizontal sectional: view::taken on :liner -lt3 of Fig. 2.

"FlgQELlS a view isimilar to Rie -4 of the secztionarplaneb'eing takenon' line 5-+-5 of "Fig.i'2.

:Fig. 6 istanwenlarged vertical sectional :view .takenithroughzone of the intermediate: refractory blocks of the lower. grate.

"Fig.7. is -.a1perspective view. of. one of the-botitonrblocksof therlowers-grate structures; and

. Figs. 8; and; 9 zero ITtQPLBIDd bottom: perspective views ofone oipthe .upper blocks of .the lower grate structure.

This. :application is a division-f. my co -pending application =Serial:No; 263;900, filed March-:22, .1928.

Referring to the drawings, .a furnace I is provided with an inclined multiple retort-.stoker :2 of theunderfeed forced draft type. The stoker v2- extends from the frontwalL-(not shown) rear- .Wardly andvdownwardly between the furnacetside Walls in .the direction of the rear -.wa1l .(not .shcwn), and terminatesin an ash pocket 5, having crushing apparatussii locatedtatitslower end.

The:-2stoker-' 2 comprlses broadly a plurality' of inclined tu$zrechambers or boxes' I; and a' corresponding -plurality of retorts 8 alternating therewithpconstituting an upper grate surface; a

plurality of movable extension grate sections- 9 disposed iri1ine with the"retorts tf and of sufficient' widthto extendsubstantially between the center lines of adjacent tuyrechar'nhers' 1K1; -a'-ipiurality =of 'ex-tension plates 1 I disposed in line "with and adjacent to the lower end of the tuyere and retortchambers'" I and 8 a' -plur a1ity of stationary lower *grate' secticns"-:l3; provided beneath *the rearwardlydisposed end of themov-able extension *grat-setionsfl and form: a downwa rdly and 'forwardly incli-n'ed wtill portiorr of the ash pdcket'-- 5* extending-across the full width thereof pu'shers 126 which: extend upwar'dly: in stepped relation from the extension plates II -Each oi -the lower grate se'ctions" i3 comprises -a: rear wal1 I 3 l a front welll fl 32 side walls L33 an'd l 3'4ya bottom wall tfl5,: and a' top wall I36.

These wallsdefine ==an upwardly -extending air 'chamberhorso called *grate -box, having alower air inlet iopening l 3i: connected sbyilmeansil of an -air duct $38 to a:main.air chamberi'l'39 positioned direetly beneath the' -tuyre and retort chamber-s T and 8. 'Ihis :upwardly extending airchamber also hasa-a main upperaai'r outlet opening I4I :through -'-which ':the 1 -air mayflpass into a grate chamber- I 42 formed: in each: extension grate secti'on'9. 'Theffront war I 32 of each lower .grate 'section comprises a mainiupper plate Ill-Figs. '2, 3 and:5, which is mounted on flanges I and M5,:2of verticalvangle irons M6 and I4! so as I to I abut against 1 vertical edges 36-and '39 of the t side :b'eams: I4, and the vertical extensions 38 -re'spectively. b'Flanges l 48 :and "I49: of these angle -irons -.arerseeuredtto.adjacent tuyre sides I5I of. plates I lwofsuccessive tuyrechambers. I. Theupper .front closure plate l-fl isfurther-secureda in po sition hy-means :ofsangle irons I SPandits, the

.ber 8. portion of the flange I44 of the angle iron I46,

front side of the plate member I43, while flanges I56 and I51 are bolted to the retort sides 31 of the beams I4, and to the adjacent sides of extensions 38 thereof. Filler bars I58 and I59 are positioned between the upper end portions of the flanges I56 and I51 of angle irons I52 and I53, respectively, and the adjacent sides of the beams I4, as shown in Fig. 5. The angle irons I52 and I53 which are positioned in alignment with the retort chambers 8, are relatively short as compared with the angle irons I46 and I41, which are disposed in alignment with the tuyere chamber 1. The pair of angle irons I46 and I41 extend from an upper edge I6I of the front closure plate I43 to a point just above bearing plate 55, while the angle irons I52 and I53 extend from the upper edge I 6| of the closure plate I43 to a lower edge I62 thereof. The lower edge I62 of closure plate I43 is spaced from the bearing plate 55, as shown in Figs. 1 and 2, so that a desired open space I63 may be obtained. The length of .the upper closure plate I43 of each grate section I3 is sufficient to permit vertical edges I64 and I65 thereof to be positioned in substantially the center line of tuyre chamber 1, I. The upper edge I6I of the closure plate I43 is positioned in desired spaced relation to the upper wall I36 of the grate chamber or box so as to form the air outlet opening I4I. In this manner the upper front wall portion of each of the lower grate sections I3 is mounted in position on the lower rear end of the steel supporting beams I4. V

The lower open portion I63 of the front wall I32 of each grate section I3 is partially closed by a pair of spaced plate members I66 and I61, Figs. 3 and 4, forming the lower air inlet opening I31, directly in alignment with the retort cham- The plate I66 is mounted on the lower while the plate I61 is similarly mounted on the angle iron I41. Filler strips I68 and I69, Fig. 4, are respectively positioned between the lower portions of the flanges I48 and I49 and the tuyre sides of the plate sections 38. Opposite vertical edges HI and I12 of the plates I66 and I61 are respectively positioned flush with the edges I64 and I65 of the upper plate member I43, while adjacent spaced edges I13 and I14 are respectively positioned flush with adjacent retortsides of successive plate extensions 38. Upper edges I15 and I16 of, lower plate members I66 and I61 are positioned in abutting relation to the lower edge I62of the upper plate I43... Lower edges I11 and I18 are positioned in spaced relation to the bearing plate 55, as shown in Fig. 2.

The lower edge portions of the lower pair of plates I66 and I61 are further supported by means of angle irons I19. Each angle iron I19 extends from the center line of one tuyere cham- -ber'1., to the center line of the next adjacent tuyere chamber as in the case of the upper plate I43. A vertical flange I8I of the horizontal angle iron I19 is secured to an inner, side of these edge portions, while a horizontal flange I82 is positioned in spaced relation to the bearing plate of the cross beam I6 to provide a transverse opening I83 extending across the width of the grate section I3. Thus, the lower front wall portion of each of the grate sections I3 is supported on the relatively long angle irons I46 and I41, which,

I in turn, are secured to the steel side plate construction I4, 38. The vertical meeting edges of successive upper and lower pairs of closure plates I43, I43 and I61, I66 may be closed by means of a vertically extending plate I84, Fig. 5, which is mounted on a front side of adjacent portions and which extends the full height of the upper and lower closure plates I43 and I66, I61.

Each of the side walls I33, I34 of each lower grate chamber comprises a pair of upper and lower frames I89 and I9I respectively, which are mounted directly in the center line of the tuyere chamber 1 over the meeting edges of successive pairs of upper and lower rear wall closure plates I43, I43 and I66, I61. These plates constitute a common wall for successive pairs of lower stationary grate sections I3. The upper plate frame I89 is provided with transversely extending spaced feet I92 which are bolted to the upper plate member I43. The lower grate frame I9I is also provided with transversely extending feet I93 and I94 which are respectivelybolted to the 'upper plate I43 and to the vertical flange I8I of the horizontal angle iron section I19. The upper and lower members I89 and I9I are slightly spaced to provide a relatively small air passage I95 therebetween. The upper grate frame I89 is provided with an upwardly projecting portion I96 having a beveled front edge I91, Figs. 1 and 2, extending downwardly and forwardly to the upper supporting foot I92.

The rear wall I3I of each grate section I3 comprises a plurality of grate blocks I98 which are disposed in side by side, as well as superimposed relation forming horizontal and vertical Each vertical row comprises a lower main supporting grate block I99, a plurality of intermediate grate blocks 2M, and an upper grate block cap .202. As shown more particularly in Figs. 1 to 3, and 6, each intermediate grate block 5 29I comprises a rear wall 2l3 and side walls 2I4 and 2I5. The rear wall 2I3 is provided with an upper vertical surface portion 2I6 and a lower, forwardly and downwardly inclined surface portion Zn. The surface portions 2I6 and 2" constitute ash abutting surfaces which are directly exposed to the furnace heat. The upper surface portion 2 I 6 is forwardly offset with respect to the adjacent inclined lower portion 2I1 of the preceding grate block 28I. In this manner a lower edge 2I8 of the rear wall 2l3 of one grate block 29I overhangs an upper edge 2I9 of the wall 2I3 'of the next grate block directly below the same,

thereby providing a plurality of overhanging shoulder portions that are so positioned as to prevent the lodging of refuse material thereon.

The side wall 2I4 is provided with a plurality of air deflecting ribs 229 that abut against air deflecting ribs 22I of the opposite wall 2| 5 of the next adjacent grate block 20I. The grate blocks I99 are provided with similar ribs, as shown in Fig. 7. These ribs extend forwardly and downwardly from the rear wall of the grate blocks and terminate in substantially horizontally extending front and end portions 222. Thus, the adjacent side walls of the grate blocks 2M, 26I and I99, I99 are maintained in desired spaced relation, and a plurality of air outlet passages 223 are also formed which extend forwardly and upwardly in a direction substantially opposite to that of the downwardly moving material in the ash pocket 5. An advantage of discharging the air in this manner is that it causes a more complete burning of such combustible as still remains in the refuse in the ash pocket 5. The air may be supplied to the air passages 223 from the air chamber of the lower grate section I3 through a plurality of apertures 224, Figs. 6 and 7, positioned forwardly of the air passages 223 in the side walls of the grate blocks. A pluare provided with recesses'25l which aresome-" maagrms rality of spaced heat radiating ribs-225s extend forwardly from an inner side 226 of the reariwa'llr of eaclI of the grate blocks'199 and; 201, eaclrrib being triangular? in cross section and extending shown in Figs; 6 a-hd'l.

The front edged the grate bldckesideswall 2 I? terminates in apair of spaced; locking: lugs: 22%,:

while the sidewall-T 215"terminates'inl apair of: spaced locking. lugs 229.

the upper plate frame member I89 is provided flange 241 in addition to the flanges- 236 and; 231; the former corresponding in dimension to'ei'ther of'the fiange portions 234 or 23-5-i" The length of the flange portions 234 and 235issi'1eh as to per-- mit the disengagement of' the pa-ir 'of lugs: 228;

228 from the plate member slight vertical 'movement.-

I 89 upon a relatively- The -'lower-plateframe i9! is provided with a locking flange 24 2 corre sponding to the flanges 236 and 2'3 1; and a-*-rela tively long flange 243 for reasons as will presently appear.

wardly of thenext'adjacent grate sectionl3.-

The upper andlower lockinglugs 229; 229 of' the other side' wall 21 5-of-'-th'e intermediate grate block 20! is provided'wi-th apairof -recesses'245i 245, which coact withlocking flanges 246- corresponding in -all respects, to the flanges 236 and" and 243', just des'cribed;-for-"the= plateframes 139- and [9L The flanges 246 =extend transversely of'a pairof upper and 'lower'pl ateplate member M3; and the horizontal an-gle-iron-- I19 respectively. The'pai rsof plates I89; I91 and 24?, zfl'thusprovidedetachable mountings for the intermediate grate b1o'cks2Ul in ayert'icalrow immediately adjacent one side" of-the' gratesections l 3.

The next vertical row of grate' bloc'ks is simi larly secured to the=spaced pairs of "frames 241,

248 and- 249, 250,- each frame having inwardly extending locking fianges 25l, Fig. 5, coacting.-

with the lockinglugs of the intermediatengrate. blocks 20! so as to permit detachment upon a relatively small vertical: movement. The? dimension of the grate sections K l 3sissuchithat theplateframes 249, 25!! are substantiallyinwalignment with the center line of theretor-tchamber. 8.-- The next vertical row of gratewblocks is supportedby the plate frames 249, 25ll.and.252, 253, while block E99 is constructed"substantiaily the-sameasthe intermediate grate "blocks 20 I'-, with-theex."- ception that a lower pair of'lu'gs 256j255jwhich" are respectively mounted on sidewalls- 251 25?;

The upper. and lower" lockinglugs-228, 228"for the side walli'2ii4 are=re spectively provided with vertical rec'esses--2'32 and' 233 adapted to receive portions 234 and 235*: of" flanges 236" and. 23:1 extending inwardly: of" the: grate section I3 from 'a-- rearedge portion 238 of I; The upper plate with a" relatively short The plate framesIBQ and I91 are al'so provided with lockingflange portions 239' which are similar to the flange portionsjust'described; but extend in the opposite direction thereto -in'- what "deeper than the recesses. of: the upper pain of? lugs; This lower pair of" recesses? 25:1 are; closedfatltheir upper endsbysupporting wallsv258" whichrenga-ge =shou1ders1'259 5 formed by enlarging or'widen-iiig' the: lower end portion of: the flange: 2435M each lower frame plate, asfshowrrin Fig.2. 'lnezlowen'grateiblocli 1| 9& '0'13? eachvertical columni is: thus" hiring or? directly supported on 5 thelower endportio'nsro'f a pair.of:lowergrate plate frames;

whileithe-fwei ght: of the remaining g-rateblocks in eachrrowis: directly carried by the lower grate block. Thei dimerision of these locking flanges aridfrecess' portions' is such. that the lower grate block I99 may also be moved 'rearwardly away from the lower grate frames upon a relativelysmall vertical movement thereof;

A rear wall 260 of each of th'e lower grate blocks I 99 is provided witm a ='flange"portion 261* that extends belowthe-lower edges of the" grate-block side walls 2'51,"25 T; An'outerside 262 01 the flange 26f" is positioned-in alignment Witlr thebeveled or inclined surface -'portion 2 l 1-; while an; inner'sid e isprovided with an oppositel beveled siirface portion 263*" adapted to abut "against" a complementary' rear"edge-portion 264 of a plat'e member; 2653' Fig." 2f," consti-tiitir'i'g, the bottom wall I35 of the grate chamber. 'Ihe'upper portion of theincI-ifie'd' wall 263 is-" p'ro'vified with a" sh'ollllder 263 which is supported -onan upper; side 26 l or the plate member 2652' thereby providing a' 1 further secondary mounting for the lower gr'ate blocks I995" It is noted that' the-vertica1 rowsofthe grate blocks define an apprexiinate'ly flat surface that is exposed to thehea'ted ashesin the pocket 5; and

that this surface isinclined downwardly and forwardly; so that an ashpoek'et' of increasing crosssectional area maybe obtained-as the ashes are removedimt'he direction-of crusherapparatus 6 positioned atthe-bottorrr of the aslr pocket'5,-Figi 1 Moreover, a plurality of air-outletopenings in this exposed surface are provided between successive'vertical' r0wsof"grate blocks; the, air being deflected as it passes into the ash pecker 5 f0r= wardly''andupward'ly in a direction opposite to that of the d'own'wardly moving refuse; Fur:

thermore; the several" grate blocks; being secured 7 in" position. without. the-use of'bolts or rivetsjmay bereadily renewed merely by 'ffirst" moving the grate block; a relatively small vertical" distance,

and then further movihgfsaid' grate block rearwardly and outwardly of P the lower-grate structure:

The loweredge 401 of e'ach of the front' walls" 321 of the grate-guard sections' is in spaced relati'on 'to the top edge of -the"upper intermediate grateblo'cks 2M, permittingthe mounting there'- between ofa rear wall 4l4-of the-*upper grateblock"'caps'-2l l2: The width of each of the grateblock-caps 202-is substantially equal to that of the intermediate grateblocks- 2M and they are so positioned as to 'cons'titute'fcontin-uations of the vertical rows of grate blocks 20 I that extend upwardly fr0m the-lower grate block" I99.- Each' of the giat'e-block'caps-202 "comprises; in addition to the flat rear' wa11 4|4aa pair'of'forwardly extend in-gside walls 415and4l6, as-sh'own' in the perspective viewsof Figs? 8'and' A lower "edge" 41""! of therea'r' wall 414, Fig; '2, ismounted'onan adjacent upper edge ofthe intermediate grate b-lock 201,- and "slightly oven hangs the adjacent, exposed face portion 2 [6" thereof; as in the case" of the-intermediate grateblocks 2U]; Edges 41' fthe 'siiie walls 415; 416' are similarlymounted on upperwages 0f the grate-block side walls 2I4,-. 2l5, respectively. Each of the side walls M5, M8 is provided with a pair of spaced projecting lugs M9 and 42!, of which the lug 4l9, immediately adjacent to the rear wall M4, is the shorter. These lugs extend beyond the edges 418 of-the side walls 415, 416 and abut against the inner, upper side portions of the adjacent side walls 2M, 2!?) of the intermediate grate-block 2B1. In-this manner, transverse movement of the grate-block cap 202 relative to the lower, supporting grate-block 2Ell is prevented. The rear pair of locking lugs 41.9 are relatively shorter than. the front pair of locking lugs 42l ,in order to decrease the upward tilting movement necessary in order to clear the lugs 2i9 of the rear wall 213 of the supporting grate-block 20 I Each of the side walls M5, M6 is provided with an angled rib 422 which abuts against the adjacent rib of the next grate-block cap 282,

thereby forming therebetween an air passage. The inclination of the rib is such that air may be deflected outwardly and upwardly, as in the case of the lower air passages 223. 'Air may be supplied to the passages formed by the ribs 422,

by reason of the presence of air-outlet openings 423 in front portions-0f the side walls M5, 416. A front side of the rear wall M4 is provided with a plurality of forwardly-extending tapered ribs 424, corresponding to the radiating ribs 225 of the lower grate-blocks.

An upper horizontal wall 425 of each of the grate-block caps 282 is positioned just below the lower edge 45'! of an adjacent grate-guard front wall 321', and it extends-forwardly to an upstanding cross-flange 425. The flange 426, Figs. 8 and 9, extends'across the full width of the rear wall M4 and slightly beyond the same at each side to provide overhanging shoulder portions, outer sides 42'! and 4281 which are positioned respectively in the plane of .the outer side of the air-deflecting ribs 422.

A rear side 426 is positioned immediately adjacent to the frontside portion 408 of the grate-guard section front wall 321, thereby preventing a rearward movement of the cap 202. An upper horizontal edge 435 of the cross-flange 426 is positioned in abutting relation to the edges 485 and 49B of the spaced locking lugs 40!), 41H and 395, 396, respectively, thereby preventing an undesirable upward movement of the grate-block cap 202. The top wall of the grate-block cap 202 may be further extended forwardly and downwardly by means of a curved portion 432, opposite edges of which are positioned in substantial alignment with the oppositeedges 421 of the upright flange 426. These edge portions abut against the adjacent edge portions of successive grate caps 2&2, forming air chambers between successive pairs of side walls M5 and MB having a rear outlet only into the ash pocket 5. A central lower edge portion of the curved wall 432 may be recessed as shown in Fig. 8.

Assuming, for example, that it is desired to replace the lower, supporting grate-block I99 in the vertical row shown in Fig. 2, the locking key associated with the grate-guard section 322 is first removed. This permits the removal of the guard plate member 324. The guard plate member 324, which prevents the rearward and upward movement of the grate-block cap 262, having been removed, the latter may be lifted vertically, disengaging the pair of lugs 4|9, 42| from the adjacent intermediate grate-block 2M, and

429 of the upright cross-flange then .rearwardly away from the lower grate structure. 1 l

Should it not be desirable to remove entirely the guard plate member 324, the latter is lifted just sufficiently to permit the locking cross-flange 425 to clear-the adjacent lower edge 40'! of the grate-guard front wall 32'l', whereupon the cap 202 is tilted slightly until the front pair of lugs 4E9 are above the adjacent upper edge of the rear wall of the supporting grate-block 20 l. The cap 282 is then moved upwardly and rearwardly from the grate structure. The remaining intermediate grate-blocks 20! may be detached from the supporting lugs on the grate-plate frames by movingthe samevertically until the lugs are detached, and then rearwardly. When the lower, supporting grate-block I99 is reached, it may be removed in a similarmanner and then replaced by a new grate block. The parts may be again replaced in the reverse order of their removal.

While the grate blocksherein described are admirably adapted to fulfill the objects primarily stated, it is to be understood that the invention is not to be limited thereto, since they may be embodied in other forms, all coming within the scope of claims which follow.

What is claimed is: 1

1. A block for a grate structure, comprising top, side and rear walls, each of said side walls having provided toward the front end thereof a substantially arcuate flange, a transverse flange extending upwardly from said top wall, a series of cooling fins extending forwardly from the front surface of said rear wall, and one or more projections depending from the lower inner surface of each of said side walls.

2. A grate block for a stoker structure comprising top, side and rear walls, a laterally extending arcuate flange provided along the top and front edges of each of said side walls, a transverse flange extending upwardly from said top wall, cooling fins provided on the inner surface of said top and rear walls, and means extending laterally from the outer surface of said side walls defining passages for draft air.

3. A grate block of the class described, comprising a substantially vertical rear wall and substantially vertical side walls arranged at an angle to said rear wall, a plurality of substantially vertical fins projecting forwardly from the front surface of said rear wall, a series of ribs extending laterally from the outer surface of each of said side walls defining passages for draft air, and locking lugs mounted on the front edge of each of said side walls.

4. A block for a lower grate structure comprising top, side and rear walls, a substantially arcuate flange provided on each of said side walls, a transverse flange extending upwardly from said top wall, a series of cooling fins extending forwardly from the front surface of said rear wall, and locking means provided on each of said side walls.

5. A grate block of the class described, comprising a substantially vertical rear wall, and

substantially vertical side walls disposed at an wall extending below the lower edges of said side walls.

6. A grate block of the class described, comprising a substantially vertical rear wall, and substantially vertical side walls disposed at an angle to said rear Wall, a plurality of substantially vertical fins projecting forwardly from the front surface of said rear wall, a series of ribs extending laterally from the outer surface of each of said side walls defining passages for draft air, locking lugs mounted on the front edge of each of said side Walls, and means providing angularly disposed surfaces on said rear wall.

'7. A grate block adapted to comprise one of a series arranged in side by side relation in a lower grate structure of a stoker furnace, said grate.

on each of said side walls for detachably secur-' ing said grate block in position.

8. A grate block for a lower grate structure of a stoker furnace, comprising a substantially vertical rear wall, and a pair of laterally spaced, sub- 7 stantially vertical side walls, a plurality of cooling fins extending forwardly from the front surfaceof said rear wall, ribs extending laterally from the outer surface of each of said side walls defining passages for draft air, and locking lugs provided on each of said side walls for detachably securing said grate block in position.

9. A grate block adapted to comprise one of a series arranged in side by side relation in a lower grate structure of a stoker furnace, said grate block comprising a substantially vertical rear wall, and a pair of laterally spaced substantially vertical side walls, each of said side walls having one or more apertures provided therein through which draft air may pass, a plurality of cooling fins extending forwardly from the front surface of said rear wall, means at the sides of said grate block for maintaining the same in spaced relation with adjacent grate blocks, and locking lugs provided on each of said side Walls for securing said grate block in position.

10. A grate block for a lower grate structure of a stoker furnace, comprising a substantially vertical rear wall, and a pair of laterally spaced, substantially vertical side walls, each of said side walls having one or more apertures provided therein through which draft air may pass, ribs projecting outwardly from each' of said side walls defining passages for draft air, a plurality of cooling fins extending forwardly from the front surface of said rear wall, and locking lugs provided on each of said side walls for securing said grate block in position.

11. A grate block of substantially U-shaped form, having a pair of vertically disposed legs integrally connected at one end thereof to a substantially vertical web, each of said legs having one or more apertures provided therein through which draft air may pass, a plurality of ,substantially vertical fins projecting from one face of said web, ribs projecting outwardly from each of said legs defining passages for draft air, and looking means provided on each of said legs for securing the grate block in position.

12. A grate block adapted to comprise one of a series in a lower grate structure of a stoker furnace, said grate block comprising a substantially vertical, rearwardly disposed wall, and a pair of side walls integral with and extending forwardly of the side edges of said rearwardly disposed wall, each of said side walls having one or more apertures provided therein through which draft air may pass, cooling fins secured to and extending forwardly of said rearwardly disposed wall, ribs projecting outwardly from each of said side walls defining passages for draft air, and means provided on said side walls for securing said grate block in position.

HERB R R S ON, 

